Hazard Scoring Methodology

Each hazard score (0–10) is composed of 2–4 weighted sub-components. All components are returned in the score_components field of every API response. The chain is always traceable: score → parameter → source publication.

Seismic activity uses the Gutenberg-Richter relation: log₁₀(N) = a - b·M, where N is the annual rate of earthquakes ≥ magnitude M. The a and b values are regionally calibrated from the USGS National Seismic Hazard Model (NSHM 2023, Petersen et al., Bulletin of the Seismological Society of America, 2024).

The Intensity Prediction Equation uses Atkinson & Wald (2007), Seismological Research Letters Vol. 78 No. 3, validated against >200,000 "Did You Feel It?" reports: MMI = 12.27 + 2.27(M-6) + 0.13(M-6)² - 1.30·log₁₀(R) - 0.00071·R + 1.95·B - 0.577·M·log₁₀(R)

Return periods are computed from 173 years of IBTrACS North Atlantic best-track data. Wind decay after landfall follows Kaplan & DeMaria (1995): V(t) = Vb + (V₀ - Vb)·exp(-α·t). Storm surge estimates use NOAA NHC SLOSH model composites.

Climate adjustment applies a 1.4× frequency multiplier based on Abatzoglou & Williams (2016), who found anthropogenic warming responsible for approximately doubling western US forest fire area 1979–2015.

Depth-damage functions from FEMA Hazus Flood Model v5.1. These are the US standard used by USACE, FEMA, and all major catastrophe modelers.

Hail scoring uses NOAA Storm Events frequency analysis and IBHS (Insurance Institute for Business & Home Safety) roof damage research. Tornado scoring uses Brooks et al. (2003) EF2+ frequency climatology from Weather and Forecasting, with nocturnal tornado risk amplification for the Southeast.

When an event activates, CivilSense generates four concentric consequence zones (Catastrophic, Severe, Moderate, Affected) to estimate the geographic extent of impact. Zone generation varies by peril:

Earthquake

Primary: USGS ShakeMap MMI contours (per-event, when available from USGS within ~20 minutes of event). Fallback: magnitude-scaled radii using attenuation relations from Atkinson & Wald (2007).

Hurricane

Primary: NHC forecast wind radii (34kt/50kt/64kt — knots, nautical miles per hour) from the official advisory, producing asymmetric zones reflecting actual wind field geometry. Fallback: Saffir-Simpson category-based radii (used only when NHC wind radii data is unavailable).

Wildfire

Primary: NIFC official fire perimeter polygon (per-event, updated twice daily). Outer evacuation and smoke zones are derived from acreage-based buffer distances.

Flood

Zone 1 uses the NWS alert polygon directly when available (per-event geometry from the National Weather Service Alerts API). Outer zones (2–4) are circular extensions from the alert centroid using a uniform 3 km step per zone, scaled by the flood severity classification (Major Flood, Flash Flood, Moderate Flood, Minor Flood).

Severe Weather

Uses NWS Storm Prediction Center polygon geometries directly (tornado/severe thunderstorm watch/warning areas).

Exposure Estimation

Population and infrastructure exposure within each zone is estimated using state-level density data (US Census Bureau 2020 for population, HIFLD archive for infrastructure, Census AHS 2021 for housing density). When available, census-tract-level sampling via the FCC Area API and Census Bureau ACS 5-Year 2022 provides more accurate local density. All exposure figures are estimates and are labeled as such.

Wind Radii Source

CivilSense uses the National Hurricane Center's advisory text product as the primary source for tropical cyclone wind radii. Advisory text products are issued by NHC forecasters and represent the official wind field estimate at the time of issuance. Once published, advisory values are immutable — they are the historical record of what was communicated to the public at that moment.

What the B-Deck Is

The NHC best-track file (b-deck, ATCF format) is a post-analysis dataset. After each advisory cycle, NHC analysts may revise wind radii values based on additional observations, satellite imagery, or reconnaissance data that arrived after the advisory was issued. The b-deck represents the NHC's best estimate of the storm's wind field at each analysis time, incorporating all available data.

How CivilSense Computes the Delta

When a b-deck entry exists at the exact same timestamp as an advisory's analysis time, CivilSense computes a per-quadrant delta for each wind radii threshold (34-knot, 50-knot, 64-knot). The delta is defined as:

delta = b-deck value minus advisory value

A positive delta means the b-deck revised the quadrant radius upward relative to what the advisory reported. A negative delta means the b-deck revised it downward.

Deltas are computed only on exact timestamp matches. Regular advisories and best-track entries follow schedules that usually differ by a few hours, so for most advisories no best-track entry exists at the same hour and no delta is produced. The timestamps align in specific cases — for example, a special advisory issued on a synoptic hour, or an intense storm whose best track is analyzed at more frequent intervals. When they do not align, no delta is computed: comparing an advisory at one hour against a best-track entry at a different hour conflates source differences with the storm's own evolution and is meteorologically invalid.

What Deltas Represent

Deltas are normal post-analysis revisions. They reflect the routine process by which NHC refines its wind field estimates as additional data becomes available. A non-zero delta is not an error in either source. It is the expected outcome of a system where real-time advisories are issued under time pressure and best-track analysis incorporates data that arrived later.

Every ingested record stores: source, source_url, ingested_at, and confidence_score. Every model parameter stores source_description with a full publication citation, validation_note, and effective_date.

Full data lineage documentation is available at /docs/data-lineage.md in the repository.

1. Petersen, M.D., et al. (2024). "The 2023 US National Seismic Hazard Model." BSSA.
2. Atkinson, G.M. & Wald, D.J. (2007). Seismological Research Letters 78(3), 362-368.
3. FEMA (2024). Hazus Earthquake Model Technical Manual v6.1.
4. FEMA (2023). Hazus Hurricane Model Technical Manual v5.1.
5. FEMA (2023). Hazus Flood Model Technical Manual v5.1.
6. Kaplan, J. & DeMaria, M. (1995). J. Applied Meteorology.
7. Knapp, K.R., et al. (2010). IBTrACS. BAMS.
8. Abatzoglou, J.T. & Williams, A.P. (2016). PNAS 113(42). DOI: 10.1073/pnas.1607171113
9. Brooks, H.E., et al. (2003). Weather and Forecasting 18.
10. Zscheischler, J., et al. (2020). Nature Reviews Earth & Environment. DOI: 10.1038/s43017-020-0060-z